Process for Tuning Via Profile in Dielectric Material

ABSTRACT

A method of forming an integrated circuit structure includes forming a first magnetic layer, forming a first conductive line over the first magnetic layer, and coating a photo-sensitive coating on the first magnetic layer. The photo-sensitive coating includes a first portion directly over the first conductive line, and a second portion offset from the first conductive line. The first portion is joined to the second portion. The method further includes performing a first light-exposure on the first portion of the photo-sensitive coating, performing a second light-exposure on both the first portion and the second portion of the photo-sensitive coating, developing the photo-sensitive coating, and forming a second magnetic layer over the photo-sensitive coating.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of the following provisionally filedU.S. Patent application: Application Ser. No. 62/748,827, filed Oct. 22,2018, and entitled “Inductors Having Magnetic Shells and Methods FormingSame;” which application is hereby incorporated herein by reference.

BACKGROUND

Inductors are important components in integrated circuits. Inductors,however, do not scale well, and the downscaling of the inductors inintegrated circuits often incurs the penalty of the downgrading inperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1-7, 8A, 8B, and 9-14 illustrate the cross-sectional views ofintermediate stages in the formation of an inductor in accordance withsome embodiments.

FIG. 15 illustrates another cross-sectional view of an inductor inaccordance with some embodiments.

FIG. 16 illustrates a cross-sectional view of a package componentshowing a metal bump in accordance with some embodiments.

FIG. 17 illustrates a top view of an inductor in accordance with someembodiments.

FIGS. 18 and 19 illustrate the absorption of photo-sensitive materialsas a function of wavelengths in accordance with some embodiments.

FIG. 20 illustrates a process flow for forming an inductor in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

An inductor and the method of forming the same in a die/wafer areprovided in accordance with some embodiments. The intermediate stages inthe formation of the inductor are illustrated in accordance with someembodiments. Some variations of some embodiments are discussed.Throughout the various views and illustrative embodiments, likereference numbers are used to designate like elements. In accordancewith some embodiments of the present disclosure, the inductor includes adielectric material separating a magnetic material from conductive linesin the inductor. The dielectric material includes a negativephoto-sensitive material, which is patterned using a double-exposureprocess followed by a single development process, and the sidewalls ofthe dielectric material have a tapered profile.

FIGS. 1 through 7, 8A, 8B, and 9 through 14 illustrate thecross-sectional views of intermediate stages in the formation of aninductor in a device wafer (and die) in accordance with some embodimentsof the present disclosure. The corresponding processes are alsoreflected schematically in the process flow 200 as shown in FIG. 20.

FIG. 1 illustrates a cross-sectional view of package component 20.Package component 20 includes a plurality of package components 22therein. In accordance with some embodiments of the present disclosure,package component 20 is a device wafer including integrated circuitdevices 26, which may include active devices and possibly passivedevices. In accordance with alternative embodiments of the presentdisclosure, package component 20 is an interposer wafer, which does notinclude active devices, and may or may not include passive devices. Inaccordance with yet alternative embodiments of the present disclosure,package component 20 is a package substrate strip, which includes aplurality of package substrates. Package component 20 may also be areconstructed wafer including a plurality of packages therein. Insubsequent discussion, a device wafer is discussed as an example packagecomponent 20, while the embodiments of the present disclosure may alsobe applied on interposer wafers, package substrates, packages,reconstructed wafers, etc.

In accordance with some embodiments of the present disclosure, packagecomponent 20 includes semiconductor substrate 24 and the features formedat a top surface of semiconductor substrate 24. Semiconductor substrate24 may be formed of crystalline silicon, crystalline germanium, silicongermanium, or a III-V compound semiconductor such as GaN, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, GaInAsP, or the like. Semiconductor substrate 24may also be a bulk semiconductor substrate or aSemiconductor-On-Insulator (SOI) substrate. Shallow Trench Isolation(STI) regions (not shown) may be formed in semiconductor substrate 24 toisolate the active regions in semiconductor substrate 24. Although notshown in FIG. 1, through-vias (sometimes referred to as through-siliconvias or through-semiconductor vias) may be formed to extend intosemiconductor substrate 24, wherein the through-vias are used toelectrically inter-couple the features on opposite sides of packagecomponent 20.

In accordance with some embodiments of the present disclosure, packagecomponent 20 includes integrated circuit devices 26, which may includesome portions formed on the top surface of semiconductor substrate 24.Integrated circuit devices 26 may include Complementary Metal-OxideSemiconductor (CMOS) transistors, resistors, capacitors, diodes, and thelike in accordance with some embodiments. The details of integratedcircuit devices 26 are not illustrated herein. In accordance withalternative embodiments, package component 20 is used for forminginterposers, and substrate 24 may be a semiconductor substrate or adielectric substrate.

Inter-Layer Dielectric (ILD) 28 is formed over semiconductor substrate24 and fills the space between the gate stacks of transistors (notshown) in integrated circuit devices 26. In accordance with someembodiments, ILD 28 is formed of Phospho Silicate Glass (PSG), BoroSilicate Glass (BSG), Boron-doped Phospho Silicate Glass (BPSG),Fluorine-doped Silicate Glass (FSG), Tetra Ethyl Ortho Silicate (TEOS)oxide, or the like. In accordance with some embodiments of the presentdisclosure, ILD 28 is formed using a deposition method such asPlasma-Enhanced Chemical Vapor Deposition (PECVD), Low Pressure ChemicalVapor Deposition (LPCVD), spin-on coating, Flowable Chemical VaporDeposition (FCVD), or the like.

Contact plugs (not shown) are formed in ILD 28, and are used toelectrically connect integrated circuit devices 26 to overlying metallines and vias. In accordance with some embodiments of the presentdisclosure, the contact plugs are formed of a conductive materialselected from tungsten, aluminum, copper, titanium, tantalum, titaniumnitride, tantalum nitride, alloys therefore, and/or multi-layersthereof. The formation of the contact plugs may include forming contactopenings in ILD 28, filling a conductive material(s) into the contactopenings, and performing a planarization (such as a Chemical MechanicalPolish (CMP) process or a mechanical grinding process) to level the topsurfaces of the contact plugs with the top surface of ILD 28.

ILD 28 and the contact plugs may be parts of interconnect structure 32.Interconnect structure 32 further includes metal lines 34 and vias 36,which are formed in dielectric layers 38 (also referred to asInter-metal Dielectrics (IMDs)). The metal lines at a same level arecollectively referred to as a metal layer hereinafter. In accordancewith some embodiments of the present disclosure, interconnect structure32 includes a plurality of metal layers including metal lines 34 thatare interconnected through vias 36. Metal lines 34 and vias 36 may beformed of copper or copper alloys, and they can also be formed of othermetals. In accordance with some embodiments of the present disclosure,dielectric layers 38 are formed of low-k dielectric materials. Thedielectric constants (k values) of the low-k dielectric materials may belower than about 3.0, for example. Dielectric layers 38 may comprise acarbon-containing low-k dielectric material, Hydrogen SilsesQuioxane(HSQ), MethylSilsesQuioxane (MSQ), or the like. In accordance with someembodiments of the present disclosure, the formation of dielectriclayers 38 includes depositing a porogen-containing dielectric materialand then performing a curing process to drive out the porogen, and hencethe remaining dielectric layers 38 are porous.

The formation of metal lines 34 and vias 36 may include single damasceneand/or dual damascene processes. In a single damascene process, a trenchis first formed in one of dielectric layers 38, followed by filling thetrench with a conductive material. A planarization such as a CMP processis then performed to remove the excess portions of the conductivematerial higher than the top surface of the corresponding dielectriclayer 38, leaving a metal line in the trench. In a dual damasceneprocess, both a trench and a via opening are formed in one of dielectriclayers 38, with the via opening underlying and connected to the trench.The conductive material is then filled into the trench and the viaopening to form a metal line and a via, respectively. The conductivematerial may include a diffusion barrier layer and a copper-containingmetallic material over the diffusion barrier layer. The diffusionbarrier layer may include titanium, titanium nitride, tantalum, tantalumnitride, or the like.

Interconnect structure 32 includes top conductive (metal) features suchas metal lines, metal pads, or vias in a top dielectric layer ofdielectric layers 38. In accordance with some embodiments, the topdielectric layer is formed of a low-k dielectric material similar to thematerial of the lower ones of dielectric layers 38. In accordance withother embodiments, the top dielectric layer is formed of a non-low-kdielectric material, which may include silicon nitride, Undoped SilicateGlass (USG), silicon oxide, or the like. The top dielectric layer mayalso have a multi-layer structure including, for example, two USG layersand a silicon nitride layer in between. The top dielectric layer issometimes referred to as a passivation layer.

Passivation layer 44 is formed over interconnect structure 32.Passivation layer 44 may be a single layer or a composite layer, and maybe formed of a non-porous material. In accordance with some embodimentsof the present disclosure, passivation layer 44 is a composite layerincluding a silicon oxide layer and a silicon nitride layer over thesilicon oxide layer.

FIG. 1 also illustrates the formation of dielectric layer 48. Inaccordance with some embodiments of the present disclosure, dielectriclayer 48 is formed of a polymer such as polyimide, polybenzoxazole(PBO), benzocyclobutene (BCB), or the like. Dielectric layer 48 is thussometimes referred to as a first polymer layer (or polymer-1) while itmay also be formed of other materials. In accordance with otherembodiments, dielectric layer 48 is formed of an inorganic dielectricmaterial such as silicon oxide, silicon nitride, silicon oxynitride, orthe like. Dielectric layer 48 may be formed of a light-sensitivematerial (such as a photo resist), which may be a negative photo resistor a positive photo resist. The formation and the patterning ofdielectric layer 48 may include a light-exposure process and adevelopment process.

FIG. 1 further illustrates the formation of stacked layers 50, 52, 54,and 56 over dielectric layer 48. The respective process is illustratedas process 202 in the process flow shown in FIG. 20. Adhesion layer 50is formed over dielectric layer 48. In accordance with some embodiments,adhesion layer 50 is formed of titanium, which has a good adhesion todielectric layer 48. Adhesion layer 50 may be formed using PhysicalVapor Deposition (PVD), Chemical Vapor Deposition (CVD), or the like.Dielectric layer 52 is formed over adhesion layer 50. In accordance withsome embodiments, dielectric layer 52 is formed of silicon nitride,silicon oxynitride, or the like. Dielectric layer 52 may be formed usingAtomic Layer Deposition (ALD), CVD, Plasma Enhance Chemical VaporDeposition (PECVD), or the like.

Etch stop layer 54 is formed over dielectric layer 52. In accordancewith some embodiments, etch stop layer 54 is formed by depositing ametal layer such as a cobalt layer, and then performing an oxidationprocess such as a plasma oxidation process, a thermal oxidation process,or the like on the metal layer, so that the metal layer is convertedinto a metal oxide layer such as a cobalt oxide layer. The etch stoplayer 54 may also be formed of a tantalum oxide layer or a titaniumoxide layer, which may be formed by depositing the corresponding metallayer, and then oxidizing the metal layer.

Magnetic layers 56 are formed over etch stop layer 54. In accordancewith some embodiments, magnetic layers 56 include magnetic film (layer)56A, magnetic film (layer) 56B over magnetic film 56A, and magnetic film(layer) 56C over magnetic film 56B, with materials of magnetic films56A, 56B, and 56C being formed of different materials. Magnetic layers56 may also include other layers and materials such as a boron layer. Inaccordance with some embodiments of the present disclosure, there is asingle composite layer including one layer 56A, one layer 56B, and onelayer 56C. In accordance with other embodiments of the presentdisclosure, there are a plurality of composite layers, each include alayer 56A, a layer 56B, and a layer 56C. Accordingly, layers 56A, layers56B, and layers 56C are formed alternatingly. The total thickness T1 ofmagnetic layers 56 may be in the range between 2 μm and 10 μm inaccordance with some embodiments. Adhesion layer 50, dielectric layer52, etch stop layer 54, and magnetic layers 56 may be deposited asblanket layers expanding throughout package component 20.

Referring to FIG. 2, etching mask 58 is formed. Etching mask 58 may be aphoto resist layer. The top view of etching mask 58 may have anelongated rectangular shape. The stacked layers including adhesion layer50, dielectric layer 52, etch stop layer 54, and magnetic layers 56 arethen etched, with the etching stopping on dielectric layer 48. Therespective process is illustrated as process 204 in the process flowshown in FIG. 20. The etching of magnetic layers 56 result in magneticlayers 56′, as shown in FIG. 3. In accordance with some embodiments ofthe present disclosure, magnetic layers 56 are etched using reactive IonBeam Etching (IBE). The etching may be implemented using Glow DischargePlasma (GDP), Capacitive Coupled Plasma (CCP), Inductively CoupledPlasma (ICP), or the like. The sidewalls of magnetic layers 56′ may beslanted, which is achieved by adjusting the parameter setting of theetching process. In the etching of magnetic layers 56, etch stop layer54 is used to stop the etching.

After the etching of magnetic layers 56, etch stop layer 54 is etched,forming etch stop layer 54′, followed by the etching of dielectric layer52 and adhesion layer 50 to form dielectric layer 52′ and adhesion layer50′, respectively. In accordance with some embodiments, the tilt angleα1 of the stacked layers including magnetic layer 56′, and possiblyadhesion layer 50′, dielectric layer 52′, and etch stop layer 54′ is inthe range between about 40 degrees and about 60 degrees. After theetching, etching mask 58 (FIG. 2) is removed. Throughout thedescription, adhesion layer 50′, dielectric layer 52′, etch stop layer54′, and magnetic layers 56′ are in combination referred to as stackedlayers 57.

Next, referring to FIG. 4, dielectric layer 60 is formed. The respectiveprocess is illustrated as process 206 in the process flow shown in FIG.20. In accordance with some embodiments of the present disclosure, theformation of dielectric layer 60 includes a blanket deposition process,followed by a patterning process. The remaining portions of dielectriclayer 60 include two portions, which may be elongated strips parallel toeach other. The cross-sectional shape of dielectric layer 60 is obtainedfrom a plane orthogonal to the longitudinal direction of the strips.Dielectric layer 60 is formed of a dielectric material, which mayinclude silicon nitride, silicon oxide, silicon oxynitride, or the like.

FIGS. 5 through 7 illustrate the formation of conductive traces. Therespective process is illustrated as process 208 in the process flowshown in FIG. 20. FIG. 5 illustrates the formation of conductive seedlayer 62, which is deposited on the structure shown in FIG. 4.Conductive seed layer 62 may be a metal seed layer. In accordance withsome embodiments, conductive seed layer 62 is a composite layercomprising a plurality of layers. For example, conductive seed layer 62may include a lower layer and an upper layer, wherein the lower layermay include a titanium layer, and the materials of the upper layer mayinclude copper or a copper alloy. In accordance with alternativeembodiments, conductive seed layer 62 is a single layer, which may be acopper layer, for example. Conductive seed layer 62 may be formed usingPhysical Vapor Deposition (PVD), while other applicable methods may alsobe used.

FIG. 5 further illustrates the formation of plating mask 64. Inaccordance with some embodiments, plating mask 64 is formed of a photoresist. Plating mask 64 is patterned to form openings 66, through whichsome portions of conductive seed layer 62 are exposed. Also, theremaining portions of dielectric layer 60 have some portions directlyunderlying openings 66, and some other portions laterally expandingbeyond the edges of the respective overlying openings 66. Next, aplating process is performed to form conductive traces 68, as shown inFIG. 6. Conductive traces 68 may be formed of a metal or a metal alloysuch as copper or a copper alloy, or the like.

After the plating process, plating mask 64 is removed in a strippingprocess. For example, when plating mask 64 is formed of photo resist,plating mask 64 may be ashed using oxygen. The portions of conductiveseed layer 62 covered by plating mask 64 is then removed. Next, theexposed portions of conductive seed layer 62 that were previouslycovered by plating mask 64 are removed through etching, while theportions of conductive seed layer 62 covered by conductive traces 68remain un-removed. The resulting structure is shown in FIG. 7.Throughout the description, the remaining portions of conductive seedlayer 62 are considered as being parts of the conductive traces 68.

FIGS. 8A (or 8B) and FIG. 9 illustrate the coating and a double-exposureprocess of photo-sensitive coating 70, which is formed of alight-sensitive material. Referring to FIG. 8A, photo-sensitive coating70 is coated, for example, through spin-on coating. The respectiveprocess is illustrated as process 210 in the process flow shown in FIG.20. In accordance with some embodiments of the present disclosure,photo-sensitive coating 70 is a negative photo resist. For example,photo-sensitive coating 70 may be a negative polyimide. Other negativephoto resists (such as photo-sensitive benzocyclobutene (BCB) orphoto-sensitive polybenzoxazole (PBO) that have low shrinkage rateduring subsequent curing process may also be used. Photo-sensitivecoating 70 is sometimes referred to as a second polymer layer (orpolymer-2). The top surface of photo-sensitive coating 70 is higher thanthe top surfaces of conductive traces 68. For example, the thickness T2of the portion of photo-sensitive coating 70 directly over conductivetraces 68 may be in the range between about 4 μm and about 8 μm inaccordance with some embodiments. Thickness T2 is selected to that thethickness T3 in the final structure shown in FIG. 14 may fall into therange between about 3 μm and about 6 μm, as discussed in subsequentparagraphs.

Further referring to FIG. 8A, lithograph mask 72 is placed over packagecomponent 20. Lithograph mask 72 includes opaque portions 72A forblocking light, and transparent portions 72B allowing light to passthrough. In accordance with some embodiments, two of the transparentportions 72B have edges flush with (or substantially flush with) therespective edges of conductive traces 68, with the offset (if any) ofthe corresponding edges being smaller than about 1 μm. The offset, ifany, may be smaller than about 20 percent of the width W1 of conductivetraces 68. One of the opaque portions 72A is vertically aligned to theportion of photo-sensitive coating 70 between conductive traces 68. Alight exposure is performed using light beam 74, so that the portions ofphoto-sensitive coating 70 directly under transparent portions 72B areexposed. The respective process is illustrated as process 212 in theprocess flow shown in FIG. 20. As a result, these portions ofphoto-sensitive coating 70 are cross-linked.

FIG. 8B illustrates the exposure of photo-sensitive coating 70 inaccordance with some other embodiments. Lithograph mask 72′ is placedover package component 20. Lithograph mask 72′ includes opaque portions72A′ for blocking light, and transparent portion 72B′ allowing light topass through. In accordance with some embodiments, transparent portion72B′ covers conductive traces 68 and the portions of photo-sensitivecoating 70 between conductive traces 68. The opposite edges oftransparent portion 72B′ are also flush with (or substantially flushwith so that the offset is smaller than about 1 nm) the respective edgesof conductive traces 68. The offset, if any, is also smaller than about20 percent of the width W1 of conductive traces 68. A light exposure isperformed using light beam 74, so that the portions of photo-sensitivecoating 70 directly over conductive traces 68 and the portion ofphoto-sensitive coating 70 between conductive traces 68 are exposed. Asa result, these portions of photo-sensitive coating 70 are cross-linked.

The light-exposure process as shown in FIG. 8A or 8B is referred to as afirst light-exposure process of a double-exposure process. FIG. 9illustrates a second light-exposure process of the double-exposureprocess. The respective process is illustrated as process 214 in theprocess flow shown in FIG. 20. It is appreciated that the order of thefirst light-exposure process and the second light-exposure process maybe inversed. In the second light-exposure process, lithograph mask 76 isplaced over package component 20. Lithograph mask 76 includes opaqueportions 76A and transparent portion 76B. In accordance with someembodiments, transparent portion 76B covers conductive traces 68 and theportions of photo-sensitive coating between conductive traces 68. Opaqueportions 76A further laterally extends beyond the respective outer edgesof conductive traces 68 by lateral distance D1. In accordance with someembodiments of the present disclosure, lateral distance D1 is greaterthan about 10 μm, and may be in the range between about 10 μm and about30 μm. Also, lateral distance D1 is equal to or greater than the heightdifference ΔH between the top surfaces of conductive traces 68 and thetop surface of magnetic layer 56′. A light exposure is performed usinglight beam 78, so that the portions of photo-sensitive coating 70directly under transparent portion 76B is exposed. As a result, theseportions of photo-sensitive coating 70 are cross-linked.

It is appreciated that the patterns of the lithography masks 72 (FIG.8A), 72′ (FIG. 8B), and 76 (FIG. 9) are designed for exposing negativephoto-sensitive coating 70. In accordance with other embodiments, apositive photo-sensitive coating may be used, and in order to expose thepositive photo-sensitive coating, the patterns of opaque portions andtransparent portions of the corresponding lithography masks may beinverted than the respective lithography mask 72, 72′, and 76.

By using the double-exposure process, a continuous portion ofphoto-sensitive coating 70 is cross-linked. The cross-linked portion isshown in FIG. 10, and the un-cross-linked portion and under-cross-linkedportions are not shown in FIG. 10. The formation of the profile of thecross-linked portion is discussed briefly as follows referring to FIGS.18 and 19.

FIG. 18 illustrates the normalized absorption rate of light energy inlight-sensitive coating 70 as a function of the wavelengths of the lightbeams used for the light exposure. The most likely wavelengths forbroadband UV-lithography are in a range between 300 nm and 450 nm, whichincludes the characteristic wavelengths of high-pressure mercury lamp at436 nm (g-line), 405 nm (h-line) and 365 nm (i-line). As shown in FIG.8, the i-line has the highest absorption rate, and with the increase inthe wavelengths, the absorption rate generally decreases. Also,according to Beer-Lambert law, the intensity of an electromagnetic waveinside a material falls off exponentially from the surface into thematerial.

FIG. 19 illustrates the total absorbed energy as a function ofwavelengths, which indicates the efficiency in the absorption of thelight energy when light beams with different wavelengths are used. Theamount of the absorbed energy also indicates the amount of cross-linksgenerated in the exposed photo-sensitive coating, and the more energy isabsorbed, the more cross-links are generated, and vice versa. Also, FIG.19 indicates that the penetration ability of light beam increases withthe increase in wavelength, and decreases with the decrease inwavelength. Accordingly, to ensure that the portions of photo-sensitivecoating 70 directly over conductive traces 68 are well cross-linked (sothat these portions are not removed in subsequent development process),the first light-exposure process (FIG. 8A or 8B) uses the light beam 74having the wavelength between about 350 nm and about 450 nm, and thelight may include any, two of, or all three of i-line, g-line, andh-line wavelengths (FIG. 18). If the wavelength is longer than 450 nm,the cross-linked portion of photo-sensitive coating 70 directly overconductive traces 68 will be too thin. If the wavelength is shorter than350 nm, the cross-linked portion of photo-sensitive coating 70 directlyover conductive traces 68 will be too thick. The first light-exposure ismainly for defining the thickness of the cross-linked portion ofphoto-sensitive coating 70.

The second exposure (FIG. 9) is mainly for defining the profile of thecross-linked portion of photo-sensitive coating 70, so that the taperededges as shown in FIG. 10 may be generated. The second light-exposureprocess uses the light beam 78 (FIG. 9) having the wavelength betweenabout 390 nm and about 450 nm, and the light may have the spectrummainly including g-line and h-line wavelengths, but not including thei-line. If the wavelength is longer than 450 nm, the slant edges wouldbe too tapered. If the wavelength is shorter than 390 nm, the slantedges would be too vertical.

Each of the first light beam 74 and second light beam 78 may be a laserbeam having a single wavelength, which falls in the aforementionedrange. Each of the first light beam 74 and second light beam 78 mayinclude wavelengths spanning across a range, which is in aforementionedrange. The corresponding light beam 74 or 78 thus may include multiplewavelengths in the aforementioned range.

After the first and the second light exposure processes as shown inFIGS. 8A (or 8B) and 9, the light-exposed photo-sensitive coating 70 isdeveloped. The respective process is illustrated as process 216 in theprocess flow shown in FIG. 20. The un-cross linked portions andunder-cross-linked portions are removed, and the adequately cross-linkedportions remain. The resulting photo-sensitive coating 70 is illustratedin FIG. 10. FIG. 10 shows that the outer portions of photo-sensitivecoating 70 on the outer sides of conductive traces 68 have slantedsidewalls 70′. The tilt angle α2 of slanted sidewalls 70′ is lesser thanabout 45 degrees, and may be in the range between about 20 degrees andabout 50 degrees. The top surface of photo-sensitive coating 70 has twosubstantially planar portions directly over conductive traces 68, and arecessed portion between the two substantially planar portions.

FIG. 11 illustrates the photo-sensitive coating 70 after a curingprocess is performed. The respective process is illustrated as process218 in the process flow shown in FIG. 20. In accordance with someembodiments, the curing process includes a thermal curing process, whichis performed at a temperature in a range between about 180° C. and about350° C. The curing duration may be in the range between about 20 minutesand about 240 minutes. As a result of the curing process,photo-sensitive coating 70 is fully solidified and shrinks. Furthermore,the portions of photo-sensitive coating 70 directly over conductivetraces 68 may be shrunk less due to better cross-linking, and the outerportions of photo-sensitive coating farther away from conductive traces68 shrink more due to worse cross-link. As a result, the tilt angle α3of slanted sidewalls 70′ is reduced to be smaller than angle α2 (FIG.10). In accordance with some embodiments of the present disclosure, tiltangle α3 is smaller than 40 degrees, and may be in the range betweenabout 10 degrees and about 40 degrees.

With tilt angle α3 being smaller than about 40 degrees, the subsequentlydeposited magnetic layer formed on the slanted sidewalls 70′ will havebetter coverage than on the otherwise vertical sidewalls. Otherwise, iftilt angle α3 is greater than 40 degrees, the subsequently formedmagnetic layer may not have acceptable conformity. Also, small tiltangle α3 results in smaller stress being generated by the curedphoto-sensitive coating 70. On the other hand, tilt angel α3 cannot betoo small, for example, than about 35 degrees. Otherwise, the sidewalls70′ may adversely extend to the sidewalls of (rather than over)conductive traces 68. In accordance with some embodiments, to make tiltangle α3 to fall into the desirable range, the light spectrum of lightbeams 74 and 78 (FIGS. 8A, 8B, and 9), the exposure energy, and thepatterns of lithography masks 72, 72′ and 76 may be adjusted.

FIG. 12 illustrates the deposition of stacked layers 82. The respectiveprocess is illustrated as process 220 in the process flow shown in FIG.20. In accordance with some embodiments of the present disclosure,stacked layers 82 includes adhesion layer 82A, dielectric layer 82B, anetch stop layer (not shown) over dielectric layer 82B, and magneticlayers 82C over the etch stop layer. The candidate materials andformation methods for forming adhesion layer 82A, dielectric layer 82B,the etch stop layer, and magnetic layers 82C may be essentially the sameas that of adhesion layer 50, dielectric layer 52, etch stop layer 54,and magnetic layers 56 (FIG. 1), respectively. The details are thus notrepeated herein. The coverage and conformity of stacked layers 82 areimproved due to the well-controlled slanted edges of photo-sensitivecoating 70.

FIG. 13 illustrates the patterning of stacked layer 82, which isachieved through etching, hence forming stacked layers 82′, whichincludes adhesion layer 82A′, dielectric layer 82B′, an etch stop layer,and magnetic layers 82C′. The respective process is illustrated asprocess 222 in the process flow shown in FIG. 20. Magnetic layers 82C′are magnetically coupled to magnetic layers 56′ through dielectric layer82B′, and magnetic layers 82C′ and magnetic layers 56′ in combinationform a shell, which can improve the inductance of the resultinginductor.

Next, as shown in FIG. 14, dielectric layer 84 is formed. The respectiveprocess is illustrated as process 224 in the process flow shown in FIG.20. In accordance with some embodiments of the present disclosure,dielectric layer 84 is formed of a polymer such as polyimide,polybenzoxazole (PBO), benzocyclobutene (BCB), or the like. Dielectriclayer 84 is thus sometimes referred to as a third polymer layer (orpolymer-3). Conductive traces 68 and the magnetic shell formed ofmagnetic layers 56′ and 82′ in combination form inductor 86. Theinductance of inductor 86 is improved due to the interaction ofconductive traces 68 and the magnetic shell 56′/82′. In subsequentprocesses, electrical connectors (such as solder regions 94 andUnder-Bump Metallurgies 92 in FIG. 16) may be formed, and packagecomponents 20 may be singulated into individual dies 22.

Referring again to FIG. 14, the portions of photo-sensitive coating 70directly over conductive traces 68 have thickness T3. Thickness T3cannot be too large. Otherwise, the resulting inductance of inductor 86is too small. Thickness T3 cannot be too small either. Otherwise, theresulting inductance of inductor 86 is too large and the reliability ofinductor 86 is degraded. In accordance with some embodiments of thepresent disclosure, thickness T3 is in the range between about 3 μm andabout 6 μm.

FIG. 15 illustrates a cross-section of the reference plane 15-15 asshown in FIG. 14. FIG. 15 illustrates the lengthwise direction ofconductive trace 68. FIGS. 14 and 15 in combination show the shape ofthe shell formed of magnetic layers 56′ and 82′.

FIG. 16 illustrates a region of package component 22, in which noinductor is formed. Accordingly, the combination of FIGS. 14 and 16reveal where inductor 86 is located in package component 22 withrelative to other features such as solder regions, metal pads, anddielectric layers. FIG. 16 illustrates metal pad 88, which may be analuminum pad, formed in passivation layer 44 and under dielectric layer48 (polymer-1). Conductive trace 90, which is also referred to as aPost-Passivation Interconnect (PPI), extends into dielectric layer 48. Aportion of conductive trace 90 is formed over dielectric layer 48.Dielectric layer 84 is formed over dielectric layer 48. Inductor 86 isinserted between dielectric layers 48 and 84 in another region that isshown in FIG. 14. UBM 92 is formed to extend into dielectric layer 84.Electrical connector 96 is formed on UBM 92. Electrical connector 96 maybe a solder region, a metal pillar, a metal pillar plus an overlyingsolder layer, or the like.

FIG. 17 illustrates a top view of inductor 86, with FIG. 14 illustratinga cross-section of the reference plane 14-14 in FIG. 17, and FIG. 15illustrating a cross-section of the reference plane 15-15 in FIG. 17. Inaccordance with some embodiments, current I1 may flow into a firstconductive trace 68, routed into underlying layers, and flow into asecond conductive trace 68 as current I1′. The inductance of inductor 86is enhanced by the magnetic shell 82′/56′.

The embodiments of the present disclosure have some advantageousfeatures. Co—Zr—Ta films have exhibited fewer resistive losses and alower permeability, while maintaining a higher saturation magnetization.The present disclosure reveals a method and the corresponding inductorincluding a magnetic shell, which may be formed of Co—Zr—Ta films. Theprofile of the dielectric layer in the inductor is patterned through adouble-exposure process, followed by a single development process, sothat the tilt angle of the sidewalls of dielectric layer is in adesirable range. This improves the coverage and the conformity of themagnetic layers over the dielectric layer. Also, with the taperedsidewalls of the dielectric layer, the stress in the resulting structureis reduced. Experiment results have revealed that if a two-sub-layerdielectric layer formed using two-coating, two-exposure andtwo-development process is adopted, the profile of the resultingtwo-sub-layer dielectric layer is unable to achieve the small tilt angleα3. Also, the stress of the device die including the two-layerdielectric layer will be greater, and the respective wafer will havegreater warpage, which may be around 600 μm. By using the embodiments ofthe present disclosure, the wafer warpage is reduced to about 400 μm.

In accordance with some embodiments of the present disclosure, a methodof forming an integrated circuit structure includes forming a firstmagnetic layer; forming a first conductive line over the first magneticlayer; coating a photo-sensitive coating on the first magnetic layer,wherein the photo-sensitive coating comprises a first portion directlyover the first conductive line; and a second portion offset from thefirst conductive line, wherein the first portion is joined to the secondportion; performing a first light-exposure on the first portion of thephoto-sensitive coating; performing a second light-exposure on both thefirst portion and the second portion of the photo-sensitive coating;developing the photo-sensitive coating; and forming a second magneticlayer over the photo-sensitive coating. In an embodiment, the firstlight-exposure is performed using a first lithography mask; and thesecond light-exposure is performed using a second lithography maskdifferent from the first lithography mask. In an embodiment, the firstlight-exposure is performed using a first wavelength, and the secondlight-exposure is performed using a second wavelength different from thefirst wavelength. In an embodiment, the first wavelength is shorter thanthe second wavelength. In an embodiment, the method further includesforming a second conductive line over the first magnetic layer, whereinthe first conductive line and the second conductive line are parallel toeach other, and wherein the second conductive line is coated in thephoto-sensitive coating. In an embodiment, in both the firstlight-exposure and the second light-exposure, an intermediate portion ofthe photo-sensitive coating between the first conductive line and thesecond conductive line is light-exposed. In an embodiment, in the firstlight-exposure, an intermediate portion of the photo-sensitive coatingbetween the first conductive line and the second conductive line is notlight-exposed, and in the second light-exposure, the intermediateportion of the photo-sensitive coating is light-exposed. In anembodiment, the first magnetic layer, the first conductive line, and thesecond magnetic layer form parts of an inductor. In an embodiment, thecoating the photo-sensitive coating comprises coating a negative photoresist. In an embodiment, the forming the first magnetic layer comprisesdepositing a cobalt layer; depositing a zirconium layer over the cobaltlayer; and depositing a tantalum layer over the zirconium layer.

In accordance with some embodiments of the present disclosure, a methodof forming an integrated circuit structure, the method includes forminga first conductive line and a second conductive line; coating aphoto-sensitive coating, which includes first portions directly over thefirst conductive line and the second conductive line; a second portionbetween the first conductive line and the second conductive line; thirdportions on opposite sides of a combined region, wherein the combinedregion comprises the first conductive line, the second conductive line,and the second portion of the photo-sensitive coating; performing afirst light-exposure to expose the first portions of the photo-sensitivecoating, wherein the first light-exposure is performed using a firstlight beam having a first wavelength; performing a second light-exposureto expose the first portions and the third portions of thephoto-sensitive coating, wherein the second light-exposure is performedusing a second light beam having a second wavelength different from thefirst wavelength; and developing the photo-sensitive coating. In anembodiment, the method further includes depositing a first magneticlayer, wherein the first conductive line and the second conductive lineare overlapping the first conductive line and the second conductiveline; and forming a second magnetic layer over the photo-sensitivecoating and the first magnetic layer. In an embodiment, the firstconductive line and the second conductive line are parts of an inductor.In an embodiment, the coating the photo-sensitive coating comprisescoating a negative photo resist. In an embodiment, the first wavelengthis in a range between about 350 nm and about 450 nm, and the secondwavelength is in a range between about 390 nm and about 450 nm.

In accordance with some embodiments of the present disclosure, anintegrated circuit structure includes a first magnetic layer; a firstconductive line and a second conductive line over the first magneticlayer and parallel to each other; and a dielectric layer comprisingfirst portions directly over the first conductive line; a second portionbetween the first conductive line and the second conductive line; andthird portions on opposite sides of a combined region, wherein thecombined region comprises the first conductive line, the secondconductive line, and the second portion of the dielectric layer, whereinsidewalls of the third portions are slanted with slant angles beingsmaller than about 40 degrees. In an embodiment, the dielectric layer isformed of a negative photo resist. In an embodiment, the first portionsof the dielectric layer have a thickness in a range between about 3 μmand about 6 μm. In an embodiment, the first magnetic layer is formed ofcobalt, zirconium, and tantalum. In an embodiment, the dielectric layeris formed of a homogenous material, with no distinguishable interfaceinside the dielectric layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method of forming an integrated circuit structure, the methodcomprising: forming a first magnetic layer; forming a first conductiveline over the first magnetic layer; coating a photo-sensitive coating onthe first magnetic layer, wherein the photo-sensitive coating comprises:a first portion directly over the first conductive line; and a secondportion offset from the first conductive line, wherein the first portionis joined to the second portion; performing a first light-exposure onthe first portion of the photo-sensitive coating; performing a secondlight-exposure on both the first portion and the second portion of thephoto-sensitive coating; developing the photo-sensitive coating; andforming a second magnetic layer over the photo-sensitive coating.
 2. Themethod of claim 1, wherein: the first light-exposure is performed usinga first lithography mask; and the second light-exposure is performedusing a second lithography mask different from the first lithographymask.
 3. The method of claim 1, wherein the first light-exposure isperformed using a first wavelength, and the second light-exposure isperformed using a second wavelength different from the first wavelength.4. The method of claim 3, wherein the first wavelength is shorter thanthe second wavelength.
 5. The method of claim 1 further comprising:forming a second conductive line over the first magnetic layer, whereinthe first conductive line and the second conductive line are parallel toeach other, and wherein the second conductive line is coated in thephoto-sensitive coating.
 6. The method of claim 5, wherein in both thefirst light-exposure and the second light-exposure, an intermediateportion of the photo-sensitive coating between the first conductive lineand the second conductive line is light-exposed.
 7. The method of claim5, wherein in the first light-exposure, an intermediate portion of thephoto-sensitive coating between the first conductive line and the secondconductive line is not light-exposed, and in the second light-exposure,the intermediate portion of the photo-sensitive coating islight-exposed.
 8. The method of claim 1, wherein the first magneticlayer, the first conductive line, and the second magnetic layer formparts of an inductor.
 9. The method of claim 1, wherein the coating thephoto-sensitive coating comprises coating a negative photo resist. 10.The method of claim 1, wherein the forming the first magnetic layercomprises: depositing a first magnetic film; depositing a secondmagnetic film over the first magnetic film; and depositing a thirdmagnetic film over the second magnetic film, wherein the first magneticfilm, the second magnetic film, and the third magnetic film are formedof different materials.
 11. A method of forming an integrated circuitstructure, the method comprising: forming a first conductive line and asecond conductive line; coating a photo-sensitive coating comprising:first portions directly over the first conductive line and the secondconductive line; a second portion between the first conductive line andthe second conductive line; third portions on opposite sides of acombined region, wherein the combined region comprises the firstconductive line, the second conductive line, and the second portion ofthe photo-sensitive coating; performing a first light-exposure to exposethe first portions of the photo-sensitive coating, wherein the firstlight-exposure is performed using a first light beam having a firstwavelength; performing a second light-exposure to expose the firstportions and the third portions of the photo-sensitive coating, whereinthe second light-exposure is performed using a second light beam havinga second wavelength different from the first wavelength; and developingthe photo-sensitive coating.
 12. The method of claim 11 furthercomprising: depositing a first magnetic layer, wherein the firstconductive line and the second conductive line are overlapping the firstmagnetic layer; and forming a second magnetic layer over thephoto-sensitive coating and the first magnetic layer.
 13. The method ofclaim 12, wherein the first conductive line and the second conductiveline are parts of an inductor.
 14. The method of claim 11, wherein thecoating the photo-sensitive coating comprises coating a negative photoresist.
 15. The method of claim 11, wherein the first wavelength is in arange between about 350 nm and about 450 nm, and the second wavelengthis in a range between about 390 nm and about 450 nm.
 16. An integratedcircuit structure comprising: a first magnetic layer; a first conductiveline and a second conductive line over the first magnetic layer andparallel to each other; and a dielectric layer comprising: firstportions directly over the first conductive line; a second portionbetween the first conductive line and the second conductive line; andthird portions on opposite sides of a combined region, wherein thecombined region comprises the first conductive line, the secondconductive line, and the second portion of the dielectric layer, whereinsidewalls of the third portions are slanted with slant angles beingsmaller than about 40 degrees.
 17. The integrated circuit structure ofclaim 16, wherein the dielectric layer is formed of a negative photoresist.
 18. The integrated circuit structure of claim 16, wherein thefirst portions of the dielectric layer have a thickness in a rangebetween about 3 μm and about 6 μm.
 19. The integrated circuit structureof claim 16, wherein the first magnetic layer is formed of cobalt,zirconium, and tantalum.
 20. The integrated circuit structure of claim16, wherein the dielectric layer is formed of a homogenous material,with no distinguishable interface inside the dielectric layer.